Light-emitting element, method for manufacturing light-emitting element, and light-emitting material

Abstract

The present invention comprises: a first chemical structure (4) that is bonded to quantum dots (3) and has general formula A; a second chemical structure (5) that is bonded to the first chemical structure (4) and has general formula B; and a third chemical structure (6) that is bonded to the second chemical structure (5) and has general formula Ca or general formula Cb.

Description

Light-emitting element, method for producing light-emitting element, and light-emitting material

[0001] The present disclosure relates to a light-emitting element, a method for producing a light-emitting element, and a light-emitting material.

[0002] Patent Document 1 discloses a quantum dot coordinated with a ligand obtained from oleic acid.

[0003] US Patent Publication 2019 / 0207137 A1

[0004] The ligand-coordinated quantum dot described in Patent Document 1 has low water resistance and low oxygen resistance, and thus has low luminous efficiency and a short lifespan. The same can be said for a light-emitting element including the ligand-coordinated quantum dot.

[0005] A light-emitting element according to an aspect of the present disclosure includes: an anode; a cathode; a quantum dot located between the anode and the cathode; a first chemical structure that is bonded to the quantum dot and has the following general formula A; a second chemical structure that is bonded to the first chemical structure and has the following general formula B; and a third chemical structure that is bonded to the second chemical structure and has the following general formula Ca or the following general formula Cb,[]

[0006] Co1 is a carboxyl group or a phosphonic acid group, La is a linear alkylene group having 1 to 18 carbon atoms, Ra is a linear alkyl group having 1 to 18 carbon atoms, L1 is an unsubstituted methylene group or an unsubstituted 1,4-phenylene group, X1 is either an atom or an oxygen atom or a sulfur atom, n1 is an integer from 1 to 12 if X1 is an atom or an oxygen atom or a sulfur atom, n2 is 0 if X1 is an atom or an oxygen atom or a sulfur atom, n2 = n1 if X1 is an oxygen atom or a sulfur atom, R1 is either hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring, R2 is either hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring. L2 is an unsubstituted alkylene group having 1 to 6 carbon atoms, or an unsubstituted arylene group having 6 to 20 carbon atoms forming the ring, and Alcoxy1 is an alkoxy group having 1 to 3 carbon atoms.

[0007] According to one aspect of this disclosure, it is possible to realize a light-emitting element with high luminous efficiency and long lifespan.

[0008] This is a cross-sectional view showing the configuration of a light-emitting element according to Embodiment 1 of the present disclosure. It shows the light-emitting material. It shows general formula A. It shows general formula B. It shows general formula Ca. It shows general formula Cb. It shows general formula B-1. It shows general formula B-2. It shows general formula B-3. It shows general formula B-4. It shows structural formula B-5. It shows structural formula Ca-1. It shows structural formula Ca-2. It shows structural formula Ca-3. It shows structural formula Ca-4. It shows structural formula Ca-5. It shows structural formula Ca-6. It shows structural formula Ca-7. It shows structural formula Ca-8. It shows structural formula Cb-1. This is a flowchart showing a method for manufacturing a light-emitting element according to Embodiment 2 of the present disclosure. This is a cross-sectional view showing the process of performing step S1. This is a cross-sectional view showing the process of performing step S2. This is a cross-sectional view showing the process of performing step S3. This is a cross-sectional view showing the process of performing step S4. This shows an overview of the thiolene reaction. This shows a specific structural example of the light-emitting material. This is a graph showing the Fourier transform infrared spectroscopy (FTIR) characteristics of the raw materials shown in Figure 25. This graph shows the spectral radiance against wavelength for quantum dots coordinated with the first, second, and third chemical structures. This graph shows the amplitude-average lifetime for quantum dots coordinated with the first, second, and third chemical structures.

[0009] The following describes the forms for implementing this disclosure. For the sake of convenience, components having the same function as those described earlier will be denoted by the same reference numerals, and their descriptions may not be repeated.

[0010] [Embodiment 1] Figure 1 is a cross-sectional view showing the configuration of a light-emitting element 101 according to Embodiment 1 of the present disclosure. The light-emitting element 101 comprises an anode 1, a cathode 2, and a light-emitting layer 53. In the light-emitting element 101, the anode 1, the light-emitting layer 53, and the cathode 2 are stacked in order from the substrate 56 and insulating layer 57 side. The light-emitting element 101 may also comprise at least one of a hole injection layer 51, a hole transport layer 52, an electron transport layer 54, an electron injection layer (not shown), and a partition wall 55. The partition wall 55 separates the light-emitting element 101 from other light-emitting elements. In the light-emitting element 101, there may be multiple layers of each of the hole injection layer 51, hole transport layer 52, light-emitting layer 53, electron transport layer 54, and electron injection layer. In the light-emitting element 101, there may be multiple partition walls 55.

[0011] Examples of materials for anode 1 include ITO (Indium Tin Oxide) and alloys of ITO and silver. An example of material for hole injection layer 51 is a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT:PSS). Another example of material for hole injection layer 51 is NiO and CuSCN. Examples of material for hole transport layer 52 include poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD).

[0012] Examples of materials for the electron transport layer 54 include ZnO and MgZnO. Examples of materials for the cathode 2 include ITO and silver.

[0013] Figure 2 shows the light-emitting material 201. Figure 3 shows general formula A. Figure 4 shows general formula B. Figure 5 shows general formula Ca. Figure 6 shows general formula Cb.

[0014] The light-emitting layer 53 has a light-emitting material 201. The light-emitting material 201 has quantum dots 3, a first chemical structure 4, a second chemical structure 5, and a third chemical structure 6. The light-emitting layer 53 is located between the anode 1 and the cathode 2. Therefore, the light-emitting material 201 is located between the anode 1 and the cathode 2, and the quantum dots 3 contained in the light-emitting material 201 are located between the anode 1 and the cathode 2. The first chemical structure 4 is bonded to the quantum dots 3 and has general formula A. The second chemical structure 5 is bonded to the first chemical structure 4 and has general formula B. The third chemical structure 6 is bonded to the second chemical structure 5 and has general formula Ca or general formula Cb.

[0015] Co1 is a carboxyl group or a phosphonic acid group. Co1 is the coordination part to quantum dot 3.

[0016] La is a straight-chain alkylene group having 1 to 18 carbon atoms.

[0017] Ra is a linear alkyl group having 1 to 18 carbon atoms.

[0018] L1 is an unsubstituted methylene group or an unsubstituted 1,4-phenylene group.

[0019] X1 is either atom-free, an oxygen atom, or a sulfur atom.

[0020] n1 is an integer from 1 to 12 if X1 does not contain an atom, and an integer from 1 to 3 if X1 is an oxygen atom or a sulfur atom.

[0021] n2 is 0 if X1 contains no atoms, and n2 = n1 if X1 contains either an oxygen atom or a sulfur atom.

[0022] R1 is one of the following: hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring.

[0023] R2 is one of the following: hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring.

[0024] L2 is an unsubstituted alkylene group having 1 to 6 carbon atoms, or an unsubstituted arylene group having 6 to 20 carbon atoms forming the ring.

[0025] Alcoxy1 is an alkoxy group having one to three carbon atoms.

[0026] The material of quantum dot 3 must be cadmium-free. Quantum dot 3 itself has low water resistance and can be damaged by moisture in the air. Conventionally, this damage resulted in low luminescence intensity and a short luminescence lifetime of the quantum dot 3 itself, leading to poor PL (Photo Luminescence) and EL (Electro Luminescence) performance of the light-emitting element. It is believed that water and oxygen in the air adhere to the surface of quantum dot 3, forming defects on the surface and trapping holes, which in turn reduces the luminescence intensity and shortens the luminescence lifetime of the quantum dot 3 itself.

[0027] According to the light-emitting element 101 of Embodiment 1 of this disclosure, the third chemical structure 6 coordinates to the quantum dot 3, thereby protecting the quantum dot 3 from moisture and reducing the affinity between the quantum dot 3 and air. Therefore, the quantum dot 3 can be protected from water and oxygen contained in the air. Consequently, a light-emitting element 101 with high luminous efficiency and long lifespan can be realized.

[0028] The third chemical structure 6 may have the general formula Cb. This allows for easy realization of the third chemical structure 6.

[0029] Figure 7 shows general formula B-1. General formula B-1 is an example of general formula B. Figure 7 also shows two specific examples of general formula B-1 (structural formula B-1-1 and structural formula B-1-2). Figure 8 shows general formula B-2. General formula B-2 is an example of general formula B. Figure 8 also shows one specific example of general formula B-2 (structural formula B-2-1). The second chemical structure 5 may have general formula B-1 or general formula B-2. This makes it easy to realize the second chemical structure 5.

[0030] X is either an oxygen atom or a sulfur atom.

[0031] Figure 9 shows general formula B-3. Figure 10 shows general formula B-4. The second chemical structure 5 may have either general formula B-3 or general formula B-4. This makes it easy to realize the second chemical structure 5.

[0032] X is either an oxygen atom or a sulfur atom.

[0033] Figure 11 shows structural formula B-5. The second chemical structure 5 may have structural formula B-5. This makes it easy to realize the second chemical structure 5.

[0034] Figure 12 shows structural formula Ca-1. Figure 13 shows structural formula Ca-2. Figure 14 shows structural formula Ca-3. Figure 15 shows structural formula Ca-4. The third chemical structure 6 has the general formula Ca, and the general formula Ca may represent any of structural formulas Ca-1 to Ca-4. This makes it easy to realize the third chemical structure 6.

[0035] Figure 16 shows structural formula Ca-5. Figure 17 shows structural formula Ca-6. Figure 18 shows structural formula Ca-7. Figure 19 shows structural formula Ca-8. The third chemical structure 6 has the general formula Ca, and the general formula Ca may represent any of structural formulas Ca-5 to Ca-8. This makes it easy to realize the third chemical structure 6.

[0036] Figure 20 shows the structural formula Cb-1. The general formula Cb may also represent the structural formula Cb-1. This makes it easy to realize the third chemical structure 6.

[0037] The first chemical structure 4 may be derived from oleic acid. "Derived from oleic acid" may be defined based on (1) to (5) below.

[0038] (1) The carbon-carbon double bond site of oleic acid has a site where it has reacted with a thiol group (corresponding to the bonding position with the second chemical structure). Note that the site of substitution of the thiol group can be either of the two carbon atoms that have the carbon-carbon double bond.

[0039] (2) In (1), the carboxyl group derived from oleic acid may be replaced with a known coordination group to the quantum dot. Other than the carboxyl group, for example, a phosphonic acid group may be used.

[0040] (3) With respect to the alkylene group site in (1) or (2) between the coordination site at the same position as oleic acid (in the case of oleic acid, this refers to the carboxyl group) and the carbon atom closest to the coordination site where the original oleic acid had a carbon-carbon double bond, the following can be said: The number of carbon atoms in the alkylene site may be changed from the 7 in the oleic acid-derived structure, and it may be a straight-chain alkylene site with 1 to 18 carbon atoms (except for 7).

[0041] (4) In any one of (1) to (3), the following can be stated with regard to the alkyl group moiety located between the carbon, which is in the site where the original oleic acid had a carbon-carbon double bond and is farther from the coordination site side, and the terminal carbon in the direction opposite to the coordination site side. The number of carbons in the alkyl moiety may be changed from 8 of the oleic acid-derived structure, and the alkyl group may be a linear alkyl group having any number of carbons from 1 to 18 (excluding 8).

[0042] (5) In any one of (1) to (4), the alkylene moiety or the alkyl moiety may each independently have a substituent attached thereto.

[0043] With respect to La described above, the carbons of the alkylene group may each independently have a substituent attached thereto. With respect to Ra described above, the carbons of the alkyl group may each independently have a substituent attached thereto. Each of these substituents may be an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a heteroaryl group having 6 to 18 ring-forming atoms.

[0044] In the case where the general formula Cb represents the structural formula Cb-1, the following can be stated. Co1 is a carboxy group; La is a linear unsubstituted alkylene group having 7 carbon atoms; a hydrogen atom is bonded to the carbon atom that forms a single bond with La; Ra is a linear unsubstituted alkyl group having 8 carbon atoms; the second chemical structure may be bonded to the carbon atom that forms a single bond with Ra. Furthermore, the general formula B may represent the structural formula B-5.

[0045] [Embodiment 2] FIG. 21 is a flowchart illustrating a method for manufacturing the light-emitting element 101 according to Embodiment 2 of the present disclosure. The method for manufacturing the light-emitting element 101 according to Embodiment 2 of the present disclosure includes steps S1 to S4.

[0046] Figure 22 is a cross-sectional view showing the process of step S1. In step S1, a first solution 8 is prepared, comprising a first organic solvent 7, a quantum dot 3, and a first chemical structure 4 having a ligand capable of coordinating to the quantum dot 3, which has a double bond between two carbon atoms. Examples of the first organic solvent 7 include octane, decane, dodecane, chloroform, and tetrahydrofuran. Other examples of the first organic solvent 7 include benzene, toluene, and chlorobenzene. In the process of preparing the first solution 8 shown in step S1, oleic acid 9 and the quantum dot 3 may be mixed with the first organic solvent 7.

[0047] Figure 23 is a cross-sectional view showing the process of step S2. In step S2, the second solution 13 is prepared by mixing the silyl source 11 and the thiol source 12 with the second organic solvent 10. Examples of the second organic solvent 10 include octane, decane, dodecane, chloroform, and tetrahydrofuran. Other examples of the second organic solvent 10 include benzene, toluene, and chlorobenzene. An example of the silyl source 11 is 3-methacryloxypropyltrimethoxysilane (MPTMS). An example of the thiol source 12 is 4,4'-thiolbenzenethiol.

[0048] Figure 24 is a cross-sectional view showing the process of step S3. In step S3, the first liquid 8 and the second liquid 13 are mixed to prepare the third liquid 14.

[0049] Figure 25 is a cross-sectional view showing the process of step S4. In step S4, the third liquid 14 is irradiated with ultraviolet light 15 to form the second chemical structure 5 and the third chemical structure 6. The wavelength of the ultraviolet light 15 may be 365 nm. The irradiation time of the ultraviolet light 15 on the third liquid 14 may be 15 minutes.

[0050] In step S4, the second chemical structure 5 and the third chemical structure 6 may be formed by a thiolene reaction caused by irradiation of the third liquid 14 with ultraviolet light 15. Figure 26 shows an overview of the thiolene reaction. The thiolene reaction can be described as a reaction that connects a thiol group with a double bond site consisting of two carbon atoms.

[0051] In step S4, the unreacted portion of the substance obtained by irradiation with ultraviolet light 15 as described above may be removed by centrifugation and dispersed in a nonpolar solvent. This may yield a raw material 58 for the light-emitting layer 53, which contains quantum dots 3 to which the first chemical structure 4, the second chemical structure 5, and the third chemical structure 6 are coordinated (hydrophobized), in other words, a light-emitting material 201.

[0052] [Embodiment 3] The light-emitting material 201 shown in Figure 2 is also included in the scope of this disclosure. That is, the light-emitting material 201 according to Embodiment 3 of this disclosure comprises a quantum dot 3, a first chemical structure 4 bonded to the quantum dot 3 and having general formula A, a second chemical structure 5 bonded to the first chemical structure 4 and having general formula B, and a third chemical structure 6 bonded to the second chemical structure 5 and having general formula Ca or general formula Cb. The third chemical structure 6 may have general formula Cb. Figure 27 shows a specific structural example of the light-emitting material 201.

[0053] [Embodiment 4] The following measurements were performed using the raw material 58 shown in Figure 25.

[0054] Figure 28 is a graph showing the Fourier transform infrared spectroscopy (FTIR) characteristics of raw material 58. In Figure 28, the horizontal axis represents wavenumber (unit: cm). －１ The vertical axis represents infrared absorption intensity (in arbitrary units). Figure 28 clearly shows that peak 59 of the infrared absorption intensity corresponds to silicon monoxide, indicating that raw material 58 contains silicon monoxide.

[0055] Figure 29 is a graph showing the spectral radiance against wavelength of quantum dot 3, to which the first chemical structure 4, the second chemical structure 5, and the third chemical structure 6 are coordinated. In Figure 29, the horizontal axis is wavelength (unit: nm), and the vertical axis is spectral radiance (unit: μW / cm²). ２ The value is ( / nm). In Figure 29, the example is a quantum dot 3 in which the first chemical structure 4, the second chemical structure 5, and the third chemical structure 6 are coordinated, and the comparative example is a quantum dot 3 in which the first chemical structure 4 is coordinated, and the second chemical structure 5 and the third chemical structure 6 are not coordinated. In Figure 29, the definitions of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are as follows.

[0056] Example 1: The example was exposed to nitrogen for 1.5 hours. Example 2: The example was exposed to air for 1.5 hours. Comparative Example 1: The comparative example was exposed to nitrogen for 1.5 hours. Comparative Example 2: The comparative example was exposed to air for 1.5 hours. In the comparative examples, when quantum dot 3 was exposed to air for 1.5 hours, the fluorescence intensity decreased by approximately 40%. In the examples, when quantum dot 3 was exposed to air for 1.5 hours, the fluorescence intensity decreased by almost 0%.

[0057] Figure 30 is a graph showing the amplitude-average lifetime of quantum dot 3 coordinated with the first chemical structure 4, the second chemical structure 5, and the third chemical structure 6. In Figure 30, the vertical axis represents the amplitude-average lifetime (unit: ns). Figure 30 shows two examples of Example 1 (Example 1-1 and Example 1-2) and two examples of Example 2 (Example 2-1 and Example 2-2). Figure 30 also shows two examples of Comparative Example 1 (Comparative Example 1-1 and Comparative Example 1-2) and two examples of Comparative Example 2 (Comparative Example 2-1 and Comparative Example 2-2).

[0058] In the comparative example, exposure of quantum dot 3 to air for 1.5 hours resulted in a fluorescence lifetime reduction of approximately 30%. In the example, exposure of quantum dot 3 to air for 1.5 hours resulted in a fluorescence lifetime reduction of less than 10%.

[0059] From the above, it was confirmed that the example exhibits higher luminous efficiency and longer lifespan compared to the comparative example.

[0060] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0061] 1 Anode 2 Cathode 3 Quantum dot 4 First chemical structure 5 Second chemical structure 6 Third chemical structure 7 First organic solvent 8 First liquid 9 Oleic acid 10 Second organic solvent 11 Silyl source 12 Thiol source 13 Second liquid 14 Third liquid 15 Ultraviolet light 101 Light-emitting element 201 Light-emitting material

Claims

1. A structure comprising: an anode; a cathode; a quantum dot located between the anode and the cathode; a first chemical structure bonded to the quantum dot and having the following general formula A; a second chemical structure bonded to the first chemical structure and having the following general formula B; and a third chemical structure bonded to the second chemical structure and having the following general formula Ca or Cb. Co1 is a carboxyl group or a phosphonic acid group, La is a linear alkylene group having 1 to 18 carbon atoms, Ra is a linear alkyl group having 1 to 18 carbon atoms, L1 is an unsubstituted methylene group or an unsubstituted 1,4-phenylene group, X1 is either an atom or an oxygen atom or a sulfur atom, n1 is an integer from 1 to 12 if X1 is an atom or an oxygen atom or a sulfur atom, n2 is 0 if X1 is an atom or an oxygen atom or a sulfur atom, n2 = n1 if X1 is an oxygen atom or a sulfur atom, R1 is either hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring, R2 is either hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring. L2 is an unsubstituted alkylene group having 1 to 6 carbon atoms, or an unsubstituted arylene group having 6 to 20 carbon atoms forming a ring, and Alcoxy1 is an alkoxy group having 1 to 3 carbon atoms, in a light-emitting element.

2. The light-emitting element according to claim 1, wherein the third chemical structure has the general formula Cb.

3. The second chemical structure has the following general formula B-1 or the following general formula B-2, X is an oxygen atom or a sulfur atom. The light-emitting device according to claim 1.

4. The second chemical structure described above has the following general formula B-3 or the following general formula B-4, The light-emitting element according to claim 1, wherein X is an oxygen atom or a sulfur atom.

5. The light-emitting element according to claim 1, wherein the second chemical structure has the following structural formula B-5.

6. The light-emitting element according to claim 1, wherein the third chemical structure has the general formula Ca, and the general formula Ca represents any of the following structural formulas Ca-1 to Ca-4.

7. The light-emitting element according to claim 1, wherein the third chemical structure has the general formula Ca, and the general formula Ca represents any of the following structural formulas Ca-5 to Ca-8.

8. The light-emitting element according to claim 2, wherein the general formula Cb represents the following structural formula Cb-1.

9. The light-emitting element according to claim 8, wherein Co1 is a carboxyl group, La is a linear, unsubstituted alkylene group having 7 carbon atoms, a hydrogen atom is bonded to a carbon atom that is single-bonded to La, and Ra is a linear, unsubstituted alkyl group having 8 carbon atoms, the second chemical structure is bonded to a carbon atom that is single-bonded to Ra.

10. The light-emitting element according to claim 9, wherein the general formula B represents the following structural formula B-5.

11. A method for manufacturing a light-emitting element according to any one of claims 1 to 10, comprising: preparing a first solution comprising a first organic solvent, a quantum dot, and a first chemical structure having a ligand capable of coordinating to the quantum dot having a double bond between two carbon atoms; preparing a second solution by mixing a silyl source and a thiol source with a second organic solvent; preparing a third solution by mixing the first solution and the second solution; and irradiating the third solution with ultraviolet light to form a second chemical structure and a third chemical structure.

12. The method for producing a light-emitting element according to claim 11, wherein in the step of preparing the first liquid, oleic acid and the quantum dots are mixed with the first organic solvent.

13. A method for manufacturing a light-emitting element according to claim 11 or 12, wherein the second chemical structure and the third chemical structure are formed by a thiolene reaction caused by irradiation of the third liquid with ultraviolet light.

14. A quantum dot, a first chemical structure bonded to the quantum dot and having the following general formula A, a second chemical structure bonded to the first chemical structure and having the following general formula B, and a third chemical structure bonded to the second chemical structure and having the following general formula Ca or the following general formula Cb, Co1 is a carboxyl group or a phosphonic acid group, La is a linear alkylene group having 1 to 18 carbon atoms, Ra is a linear alkyl group having 1 to 18 carbon atoms, L1 is an unsubstituted methylene group or an unsubstituted 1,4-phenylene group, X1 is either an atom or an oxygen atom or a sulfur atom, n1 is an integer from 1 to 12 if X1 is an atom or an oxygen atom or a sulfur atom, n2 is 0 if X1 is an atom or an oxygen atom or a sulfur atom, n2 = n1 if X1 is an oxygen atom or a sulfur atom, R1 is either hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring, R2 is either hydrogen, an unsubstituted alkyl group having 1 to 6 carbon atoms, or an unsubstituted aryl group having 6 to 20 carbon atoms forming the ring. L2 is an unsubstituted alkylene group having 1 to 6 carbon atoms, or an unsubstituted arylene group having 6 to 20 carbon atoms forming a ring, and Alcoxy1 is an alkoxy group having 1 to 3 carbon atoms, in this light-emitting material.

15. The luminescent material according to claim 14, wherein the third chemical structure has the general formula Cb.

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